1. Field of Invention
The field of the claimed invention is the separation of solid waste from water used in flushing livestock flush lanes.
2. The Background Art
On dairy farms, dairy cows eat and walk on concrete flush lanes. )While in these lanes, the cows excrete solid and liquid waste, approximately 15 to 20 gallons of solid waste per cow per day. The solid waste is a valuable commodity and is used for fertilizing as well as creating bedding for cows. Thus, dairy farms pump water from large storage lagoons into the dairy cow flush lanes in order to flush the lanes and collect the solid and liquid waste, in a storage pit from which it is mixed and pumped over a screen separator to remove the solids from the water.
It is known in the art to pump the flushed water, that is water that has already been flushed down the dairy cow flush lane, to a solid waste separator. One known method of separating the solid waste is to use a metal screen filter, onto which the flushed water is pumped. The water passes through the metal screen while a percentage of the solid waste remains on the top surface of the metal screen filter. The solid waste slides off the screen onto a solid waste storage slab. The solid waste then can be removed from the storage slab and used for fertilizer, or it may be further processed into a compost heap to make a more valuable form of fertilizer. Once a percentage of solid waste is removed from the flushed water, the flushed water is drained into a storage lagoon. The flush cycle repeats by pumping water from the storage lagoons down the dairy cow flush lanes.
FIG. 1 shows a known method of flushing dairy cow flush lanes and separating solid waste from the flushed water. Water is stored in the storage lagoon 110. Flush pump 120 pumps water from the storage lagoon to the dairy cow flush lanes 130. Flushed water drains from the dairy cow flush lanes to a mixing pit and is then pumped by an agitator pump 140 to the solid waste separator 150. The solid waste separator 150 separates a percentage of the solid waste from the flushed water, whereupon the waste is deposited onto the solid waste storage slab 160. The processed flushed water is then drained from the separator 150 back to the storage lagoon 110. The arrows in FIG. 1 indicate the direction of the flow in the water lines.
A typical dairy farm may have 5,000 dairy cows, and 35 dairy cow flush lanes. A typical flush pump has a 2200 gallon per minute capacity. Usually, each dairy cow flush lane has a flush lane valve, which opens for each lane for 5 minutes at a time during each flush cycle. Thus, 2,200 gallons per minute is flushed down each flush lane for 5 minutes, thereby using 11,000 gallons per flush cycle per lane. Since a typical dairy farm has approximately 35 flush lanes, and a typical dairy farmer flushes at least 4 times a day, and each cow produces 15 gallons of waste per day, the following equation gives the amount of water that must be processed at the solid waste separator:             11,000        ⁢          xe2x80x83        ⁢          gal      lane        xc3x97    35    ⁢          xe2x80x83        ⁢    flush    ⁢          xe2x80x83        ⁢    lanes    xc3x97    4    ⁢          xe2x80x83        ⁢          flushes      day        +      "AutoLeftMatch"                  15        ⁢                  xe2x80x83                ⁢                              gal            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢            waste                    cow                xc3x97                  5,000                ⁢                  xe2x80x83                ⁢                  c          ⁢          ows                    =                        1,615,000                ⁢                  xe2x80x83                ⁢                  gal          day                    
Thus, 1,615,000 gallons of water per day must be pumped and processed through the solid waste separator before the water is redirected back to the storage lagoon.
FIG. 2 shows a schematic of a solid waste separator, the flushed water in the known dairy cow flush lane system is pumped directly to the solid waste separator 200. The flow of the pumped flushed water into the solid waste separator is shown by the arrow 210. The flushed water then flows down the metal screen filter 230, which allows the water to pass through, but stops the solid waste 250 from flowing through the metal screen filter. A series of clean water spray nozzles 220 are installed over the surface of the screen to keep the surface and the solids moist between each cycle of using the separator, thus preventing the solid waste from drying and sticking to the screen surface and insuring good operating conditions at the beginning of the next cycle. The flushed water, having been processed through the metal screen filter 230, drains out to the storage lagoon, the flow of the processed flushed water is indicated by arrow 260.
FIG. 3 shows a solid waste separator 200 coupled to a conveyor system 300. The conveyor system adds one more step in the processing of the solid waste, by moving the solid waste 310, which came from the solid waste separator 200, up a screen conveyor 320. The conveyor moves the solid waste into a spring loaded tunnel press 330, which removes excess water from the solid waste. The excess water drains to either the process pit or the storage lagoon through pipe 350. The solid waste drops and stacks into a solid waste stack 340. This extra step allows the solid waste to stack higher and drier. The drier the solid waste is, the easier it is to move and it is easier to convert to a compost stack. Compost is a more valuable form of fertilizer.
A problem in the prior art dairy cow flush lane system, is that the flushed water drained from the solid waste separator often contains a high percentage of solid waste. This is due to the fact that the more diluted the solid waste in the water is, the less efficient the metal screen filter is in removing solid waste from the flushed water. Water that contains 0.5% solid waste does not filter as efficiently as water that contains 2% solid waste. This results in dirty water being drained into the storage lagoon. After each flush cycle, the storage lagoon collects more solid waste. Methane gas buildup occurs in the storage lagoon, and the gas is then released into the atmosphere, causing pollution. The water in the storage lagoon is also used to fertilize fields, once the storage lagoon becomes too dirty, the fields and crops can be damaged by the high content of solid waste in the water. Also, as the storage lagoon water contains more solid waste, it becomes more difficult to properly flush the dairy cow flush lanes with the storage lagoon water that already has high levels of solid waste material. Another drawback to the typical dairy cow flush lane system, is that for every gallon pumped down the flush lane, that same amount of water must first be pumped through a solid waste separator pump, plus any waste collected to the solid waste separator, before being drained back to the storage lagoon. This means that a solid waste separator pump must run for long periods of time due to the high volume of flushed water used and solid waste resulting from flushing the dairy cow flush lanes. Thus, because the solid waste separator pump runs for such a long period of time, there are associated high energy costs of running the pump plus higher maintenance and repair cost.
The present invention relates to a method for flushing dairy cow flush lanes where a processing pit is used to reduce the total amount of flushed water that must be sent to a solid waste separator every day, thereby reducing energy costs and improving the efficiency of the solid waste separator. The method includes flushing dairy cow flush lanes from a processing pit, draining the flushed water back into the same processing pit and reusing the same water to flush many lanes to increase the amount of solid waste in the recycled water before pumping the water from the processing pit to a solid waste separator, draining water from the solid waste separator to a storage lagoon or back to the processing pit. Water from both the storage lagoon and processing pit is pumped to the dairy cow flush lanes, where the process repeats.
The present invention also relates to an apparatus for flushing dairy cow flush lanes comprising a first flush pump that pumps water from a storage lagoon into dairy cow flush lanes for a first pre-selected amount of time during a day, a second flush pump that pumps water from a processing pit into the dairy cow flush lanes for a second pre-selected amount of time during a day. After a flush cycle, when the water in the process pit reaches a pre-selected maximum level, a water sensor level switch activates an agitator pump that pumps water from the process pit to a solid waste separator. When the water in the process pit reaches a pre-selected minimum level, the water sensor level switch deactivates the agitator pump, thus stopping the pumping of water from the process pit to the solid waste separator.
The features mentioned in the subclaims relate to further developments of the solution according to the invention. Further advantages of the invention are found in the following detailed description.